1968 GTS 340 with Carter AVS 4966S

Hi guys, I just finished rebuilding my Carter carburetor for my 1968 Dodge Dart GTS with 340 engine. The carb is exactly a 4966S which should be for 1969 models I guess but please correct me if I am wrong.
I bought a rebuild kit from Walker and there was also a quite thick kind of base plate. This one was not in place when I removed the carb so I am not sure if I have to use it and if so at which position with respect to the gasket. Attached please find some pics of the plate, my intake manifold and the carb. Would be great if someone can help!
Thanks in advance,
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